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Potato Virus Y

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Photo credit: Bruce Watt, University of Maine, Bugwood.org

Potato virus Y (PVY) complex causes disease in many types of plants and crops

including potato, tomato, pepper, tobacco, and eggplant. Symptoms range from mild

yellow mottling on leaves to tuber necrosis (dying cells), which eventually kills the

plant. Some plants don't show any symptoms, which makes it difficult for seed
growers to remove diseased plants and leaves whole fields vulnerable to infection.

PVY does not harm people or animals.

PVY is widespread in Europe and has been present in Canada and the United States

for decades. There are three strains: a common strain (PVYO) and two necrotic

strains (PVYN and PVYNTN). The necrotic strains pose a significant threat to the U.S.

potato industry and seed trade. APHIS classifies all PVY strains as nonquarantine

regulated pests.

What To Look For

Symptoms vary depending on the strain, the plant variety, and environmental

conditions. 

The common strain, PVYO, causes a mosaic pattern in the leaves of infected

plants.

This appears as a green and yellow variation (yellow flecking) but can also

show up as a roughness in the leaves.

PVYO reduces yield but doesn't affect tubers (thick, fleshy part of the stem

that grows underground).

The necrotic strains (PVYN and PVYNTN) affect tuber quality in a way that is

hard to remedy.

On potato crops, look for raised rings of darker brown or reddened skin

around the tuber eyes. This damage may also extend into the tuber flesh.

On tobacco, you may see a veinal necrosis (when a plant's veins turn a

dark color, usually brown or black).

PVY Complex

PVY occurs as a complex of virus strains, some of which can be

distinguished by reactions on tobacco and potato cultivars and by various

laboratory diagnostic assays. Recognized strains covered by the

Canada/U.S. Management Plan for Potato Viruses That Cause Tuber

Necrosis (42.44 KB) include, but are not limited to, those described in the

Definitions and Description Section of the management plan.
PVY

Strain

Foliar

Symptoms–Tobacco

1

Foliar

Symptoms–Potato

2

Tuber

Symptoms–Potato

3

Serological

Reaction4

PVYO Mild mosaic

Severe mosaic

Vein necrosis

Leaf drop

No symptoms3

4C3 – pos

MAb2 – pos

1F5 – neg

SASA N –

neg

PVYO5 Mild mosaic

Severe mosaic

Vein necrosis

Leaf drop

No symptoms3

4C3 – pos

MAb2 – pos

1F5 – pos

SASA N –

neg

PVYN Vein necrosis Mild mosaic No symptoms3

4C3 – pos

MAb2 – neg

1F5 – pos

SASA N –

pos

PVY

NTN Vein necrosis Mild mosaic Tuber necrosis

4C3 – pos

MAb2 – neg

1F5 – pos

SASA N –

pos
PVY

Strain

Foliar

Symptoms–Tobacco

1

Foliar

Symptoms–Potato

2

Tuber

Symptoms–Potato

3

Serological

Reaction4

PVY

NE11

Vein necrosis

Mild mosaic

Mild mosaic Tuber necrosis

4C3 – pos

MAb2 – neg

1F5 – pos

SASA N –

pos

PVYE Mosaic Mild mosaic Tuber necrosis

4C3 – pos

MAb2 – neg

1F5 – pos

SASA N –

pos

PVYNWi

(N:O)

Vein necrosis Mild mosaic No symptoms3

4C3 – pos

MAb2 – pos

1F5 – neg

SASA N –

neg

1. These are typical symptoms for most virus isolates belonging to the strain, but

exceptions have been noted.

2. These are common symptoms, but symptom type and severity will vary among

cultivars and among virus isolates within each strain.

3. While most isolates of PVYNTN, PVYNE11, and PVYE induce some degree of potato

tuber necrotic ringspot disease, a limited number of virus isolates from any strain
can induce tuber necrosis symptoms in some potato cultivars.

4. ELISA using monoclonal antibodies 4C3, Mab2, and 1F5 originally described by

Ellis et al. and commercially available from Agdia, Inc. and Science & Advice for

Scottish Agriculture, Edinburgh, Scotland.

In general, the necrotic strains tend to cause a milder mosaic symptom than PVYO in

potato.

Potato Virus Y Photo Gallery

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Show Info

PVY symptoms on potato plant leaves. Bruce Watt, University of Maine, Bugwood.org

PVY symptoms on a tobacco leaf. R.J. Reynolds Tobacco Company, Bugwood.org

Raised rings of darker brown or reddened skin around potato tuber eyes. This

damage may also extend into the tuber flesh. P.M. Baldauf, S.M. Gray, and K.L.

Perry, Department of Plant Pathology, Cornell University and USDA Agricultural

Research Service

How To Prevent This Pest

PVY spreads naturally by aphids and sap-sucking insects. It can also spread to plants

on contaminated tools or equipment or by touching healthy plants after handling

infected plants. This type of disease spread is difficult to prevent. Insecticides may

help to reduce aphid populations, but these treatments will not kill all virus-carrying

aphids and transmission of the virus will continue.

Using certified seed potatoes that are low in virus levels is the best method available

to control PVY strains in the potato industry. Knowing which plant varieties are

susceptible and how symptoms appear in the varieties you grow is also important.

How It Is Treated

There is no cure for PVY-infested host plants. Once a plant is infected, it stays

infected for life and the virus can spread through the mother plant to tubers

produced by the mother plant. The best defense against PVY is to use high-quality

certified seed and to follow best management practices.

Virus Management Methods

In-Vitro Material
All plants in a tissue culture bank or introduced into tissue culture must be

tested with an ELISA that uses antibodies known to react with all PVY strains. All

plants must be found free of PVY.

Protected Environment (greenhouse, screenhouse, or growth chamber)

Seed potato production in a protected environment will be tested at least

annually for PVY.

Any crop or lot grown in a protected environment that tests positive for PVY

must be destroyed if it is found to be PVYNTN; it can be downgraded if found to

be infected with another strain of PVY.

If aphid vectors are detected in the protected environment when the crop is

growing, testing must be conducted to determine freedom from PVY.

Field-Grown Seed

All seed transported across State boundaries must be certified by the State in

order to be entered into the certification process or sold as seed for use in

commercial production.

Report Plant Pests and Diseases

Have you seen this pest or signs of pest damage? Immediately report your findings.

If your State has a seed certification agency, please report your findings to that

agency as well. 

Find your State plant regulatory official

Find your State plant health director

Controlling Potato Virus Y

Current Status

PVY is a nonquarantine regulated pest in the United States.

The necrotic strain PVYN was first reported in Canada in the 1990s and in the Pacific

Northwest of the United States in 2002. It then spread to other regions of the United

States and several Canadian provinces.
APHIS' Response

After the first report of PVYN in Canada in the early 1990s, the United States and

Canada implemented a PVYN Management Plan. We later revised and expanded the

plan to include other emerging viruses that can cause tuber necrosis in potato. The

Canada/U.S. Management Plan for Potato Viruses That Cause Tuber Necrosis (42.44

KB) includes management methods for PVY, potato mop top virus, and tobacco rattle

virus.

The plan helps to facilitate the trade of potatoes within and between the United

States and Canada while protecting the potato industry from these viruses. We work

with industry on an annual basis to review and refine management strategies and

research needs listed in the plan.

Regulatory Information

All field-grown potato seed transported across State boundaries must be Statecertified in order to be entered into the certification process or sold as seed for use

in commercial production. For more information, contact your State potato seed

certification agency.

Information for Diagnosticians

Testing

Detection and diagnosis of PVY strains is difficult. Currently, there isn't one method

that separates all strains into their respective types. Serology can distinguish

between PVYO and PVYN but doesn't separate N from NTN strains.

A tobacco bioassay remains the best method to identify necrotic isolates. However,

to confirm NTN, this test requires a tuber grow out on sensitive potato cultivars

under standard conditions. (Environment and cultivar may affect the development of

tuber necrotic symptoms.)

Finally, many primer sets have been developed for use in RT-PCR tests, but they

may not detect all possible strains.